Acute kidney injury (AKI) is a common complication in intensive care unit (ICU) patients. Renal replacement therapy (RRT) is the major supportive treatment of AKI. Despite progress in RRT management, mortality remains high and the timing of its initiation remains open to debate when no metabolic disorder (severe hyperkalemia or metabolic acidosis) or major fluid overload threaten short-term prognosis. Such abnormalities mandate RRT and are non-inclusion criteria of our study. Whereas many studies have focused on RRT modalities, no prospective randomized study has evaluated the criteria for initiating RRT in ICU in the absence of the above-mentioned life-threatening disorders. In other words, whether duration of oliguria/anuria and/or value of serum urea/creatinine are an adequate indication for RRT is unknown. Given the lack of high quality data, it is not surprising that survey of practices showed wide variation in the timing of RRT initiation and that no precise guidelines could be drawn by expert recommendation as to the optimal start of RRT, making a randomised controlled study of timing of RRT both desirable and ethical.